[Task]: Migrate BigQuery v2 Client to Python Client Library

### What needs to happen?

The BigQuery v2 client used in the Python SDK is currently generated by apitools and needs to be migrated to the [BigQuery python library](https://docs.cloud.google.com/python/docs/reference/bigquery/latest)

### Issue Priority

Priority: 2 (default / most normal work should be filed as P2)

### Issue Components

- [x] Component: Python SDK
- [ ] Component: Java SDK
- [ ] Component: Go SDK
- [ ] Component: Typescript SDK
- [ ] Component: IO connector
- [ ] Component: Beam YAML
- [ ] Component: Beam examples
- [ ] Component: Beam playground
- [ ] Component: Beam katas
- [ ] Component: Website
- [ ] Component: Infrastructure
- [ ] Component: Spark Runner
- [ ] Component: Flink Runner
- [ ] Component: Samza Runner
- [ ] Component: Twister2 Runner
- [ ] Component: Hazelcast Jet Runner
- [ ] Component: Google Cloud Dataflow Runner